From 74a335a07a17d131b9263bfdbdcb5e40673ca9ca Mon Sep 17 00:00:00 2001
From: Harold Huang <baymaxhuang@gmail.com>
Date: Thu, 3 Mar 2022 10:24:40 +0800
Subject: [PATCH] tuntap: add sanity checks about msg_controllen in sendmsg
Git-commit: 74a335a07a17d131b9263bfdbdcb5e40673ca9ca
Patch-mainline: v5.18-rc1
References: git-fixes

In patch [1], tun_msg_ctl was added to allow pass batched xdp buffers to
tun_sendmsg. Although we donot use msg_controllen in this path, we should
check msg_controllen to make sure the caller pass a valid msg_ctl.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fe8dd45bb7556246c6b76277b1ba4296c91c2505

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20220303022441.383865-1-baymaxhuang@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/tap.c   |    3 ++-
 drivers/net/tun.c   |    3 ++-
 drivers/vhost/net.c |    1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1198,7 +1198,8 @@ static int tap_sendmsg(struct socket *so
 	struct xdp_buff *xdp;
 	int i;
 
-	if (ctl && (ctl->type == TUN_MSG_PTR)) {
+	if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
+	    ctl && ctl->type == TUN_MSG_PTR) {
 		for (i = 0; i < ctl->num; i++) {
 			xdp = &((struct xdp_buff *)ctl->ptr)[i];
 			tap_get_user_xdp(q, xdp);
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2489,7 +2489,8 @@ static int tun_sendmsg(struct socket *so
 	if (!tun)
 		return -EBADFD;
 
-	if (ctl && (ctl->type == TUN_MSG_PTR)) {
+	if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
+	    ctl && ctl->type == TUN_MSG_PTR) {
 		struct tun_page tpage;
 		int n = ctl->num;
 		int flush = 0;
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -473,6 +473,7 @@ static void vhost_tx_batch(struct vhost_
 		goto signal_used;
 
 	msghdr->msg_control = &ctl;
+	msghdr->msg_controllen = sizeof(ctl);
 	err = sock->ops->sendmsg(sock, msghdr, 0);
 	if (unlikely(err < 0)) {
 		vq_err(&nvq->vq, "Fail to batch sending packets\n");